Recently, rice cookers for cooking rice with high power for enhancing the rice cooking performance have been developed and distributed widely. There are also rice cookers capable of cooking rice at different levels of softness by the same amount of water.
Conventionally, this kind of rice cooker was composed as shown in FIG. 8. In FIG. 8, a body (rice cooker main body) 1 is a cylindrical structure having an open top, and inside of the body 1 is disposed a protective frame 2 which accommodates an inner pan 3. The protective frame 2 is a cylindrical structure with a bottom made of nonmetallic material, and the upper end of the protective frame 2 is engaged with the inner circumference of the upper end of the body 1.
The inner pan 3 has a flange 4 projecting outside at the opening of the upper end, and this inner pan 3 is disposed detachably in the protective frame 2, by mounting the flange 4 on the top of an upper frame 5 in a suspended state. At the outside of the protective frame 2, an induction coil 6 for heating the inner pan 3 is disposed, and this induction coil 6 is supported by a coil cover 7 formed of a heat resistant resin material in the lower part of the outer circumference of the protective frame 2 so that the distance to the outer circumference of the inner pan 3 may be constant. In the center of the induction coil 6, a pan sensor 8 for detecting the temperature of the inner pan 3 is disposed.
An outer lid 9 made of synthetic resin is rotatably supported on a hinge member 10 formed integrally on the top of the upper frame 5 through a pin 11. An inner cover 12 is affixed at the inside of the outer lid 9. A heat releasing plate 13, being a heating element, is fixed to the inner cover 12, and an induction coil 15 supported by a coil support stand 14 is positioned on the top of this heat releasing plate 13. By the electromagnetic action of this induction coil 15, the heat releasing plate 13 generates heat. To this heat releasing plate 13, a lid sensor 16 for detecting the temperature of the heat releasing plate 13 is directly adhered with an aluminum tape, and the temperature of the heat releasing plate 13 is detected.
An engaging member 17 is positioned on the opposite side of the hinge member 10 and is formed integrally on the upper end of the protective frame 2, and confronting to this engaging member 17, an engaging lever 18 is rotatably supported on the outer lid 9 through a lever pin 19. A pan packing 20 is to enclose the inner pan 3 by pressing to the flange 4 of the inner pan 3 when the outer lid 9 is closed. A steam tube 21 provided in the center of the outer lid 9 is to prevent rice gruel from boiling over to outside.
A control board 22 is to control power feed to the induction coils 6, 12, and also control input and output of signals from the pan sensor 8 and lid sensor 16 and signal of operation display unit 23 provided before the top of the body 1. A cooling fan 24 is to cool the induction coil 6 and control board 22. The control board 22 judges the amount of rice and water in the inner pan 3 in the rice cooking amount judging process while cooking rice by the temperature detection signal from the lid sensor 16, and determines the power feed state to the induction coil 6 depending on the result of judging.
In the conventional rice cooker having such constitution, however, when detaching or attaching the inner pan 3, it is necessary to open or close the outer lid 9, and particularly when closing the outer lid 9, the front side of the body 1 on the top of the outer lid 9 must be held down. At this time, if the operation display unit 23 is located on the top of the outer lid 9 in a range possibly held by hand, an operation key may be pressed by mistake.
In such rice cooker, if the outer lid 9 is opened in the midst of cooking rice, the lid sensor 16 cannot detect the temperature in the inner pan 3 correctly, and the rice cooking amount cannot be judged normally, so that optimum rice cooking suited to the rice cooking amount is not guaranteed.
Moreover, since the heat is high, to cook the rice soft, in particular, if more water is added than usual for cooking rice, it often causes boiling-over.